1. Technical Field
The present invention relates to a technology for incising or excising living tissue by injecting pressurized liquid toward the living tissue.
2. Related Art
A technology for incising or excising tissue by pressurizing liquid such as water or physiologic saline and injecting the liquid from an injection nozzle toward the living tissue in a restricted state is developed (JP-A-2005-152127). This technology enables incision of tissue such as internal organ exclusively without damaging vascular structures such as blood vessels, and causes less damage to peripheral tissues. Therefore, burdens on patients can be reduced.
There is also proposed a technology configured to inject a pulsed jet stream intermittently when injecting liquid instead of injecting continuously from an injection nozzle, so that incision of the living tissue is enabled with a small amount of liquid injection (JP-A-2008-082202). In this technology, liquid to be injected is supplied to a small liquid chamber, and then pressurizing the liquid by reducing the volume of the liquid chamber instantaneously, thereby injecting liquid from the injection nozzle in a pulsed manner.
In order to inject the liquid from the injection nozzle, it is required to constantly supply the necessary and sufficient amount of liquid to the liquid chamber so that the liquid chamber is filled with the liquid. If air bubbles are entrained in the supplied liquid, even when the volume of the liquid chamber is reduced for injecting the liquid, the entrained air bubbles are crushed. Consequently, the liquid in the liquid chamber cannot be injected adequately by pressurizing liquid. Therefore, in the technology for injecting a pulsed jet stream, a volume variable pump which is capable of securing a sufficient flow rate without generating air bubbles is used as a pump for supplying the liquid in the liquid chamber instead of a centrifugal pump which is subject to generation of air bubbles.
However, since the liquid supply pressure is apt to vary when using the volume variable pump, there is a problem such that the operation of the liquid injection device is difficult. It is because the amount of liquid injected from the injection nozzle varies if the liquid supply pressure varies, and hence the incising capability varies or a reaction force that an operator feels when the liquid is injected varies. Therefore, in a technology for injecting liquid in a pulsed manner, it is obliged to use a specific pump which causes minimum pressure variations even though it is a volume variable type.